Ratings of small speakers

[neptune]

As you can see i have a pic of three speakers,
the two big ones have ratings of 8 ohm and 0.25 watt , the small one has nothing written over it.
what could be its ratings ?

 

[JimB]

The impedance of the small speaker is anybodies guess, it could be anything.
To find out you would have to measure it.

As for the power rating, as a first estimate it is half the size (diameter) of the other two so it may be a reasonable assumption that its power rating is one quarter (ish), say somewhere between 50 and 100mW.

JimB

 

[transistor495]

Small one looks like the driver from an earphone unit with 32Ω impedance probably with around 50mW safe power handling.

 

[audioguru]

Cell phones have low power small "speakers" like that. They produce squeaky sounds with no low frequencies.

 

[Sceadwian]

You don't have to guess the impedance of a speaker, all you need is a multimeter set to measure low ohmic resistance. The impedance of those size speakers could be in a wide range from 8-60 ohms or thereabouts, I have many dozens of such speakers, and they do look like headphone drivers, close to 32ohms as transistor495 said, not sure why but headphone drivers tend to use that clear plastic diaphragm material. There is no point is guessing power output at that size it's irrelevant, if you can hear it it's okay.

If you want to evaluate a speakers output power then the easiest method is to simply test it with a good ear in the enclosure it will be in, increase the volume until you can hear distortion that you don't like, back off 10% and calculate practical power from that.

Cell phones have low power small "speakers" like that. They produce squeaky sounds with no low frequencies.

audioguru, I am publicly upset with your statement as such is not the case, and your name being 'audioguru' you should know better than making such broad misleading statements especially to someone trying to learn something, provide information or keep your negativity to yourself.

Aside from the frequency limitations of the size of the speakers making lows very difficult to produce cell phones and the devices these types of speakers are put into are seldom constructed around a good audio cavity. That speaker WILL produce solid low frequencies in the same power output range as it does it's mid and high tones IF it's put in the proper speaker cabinet, which would be many times larger than the speaker for free air speakers.

Them being headphone drivers they did produce bass, because the air cavity between the ear muff and the ear itself acted as the resonant cavity.

It sure isn't high fidelity but I have a multimedia cell phone that was designed with the speakers in mind, enough so that placed flat on a solid object the internal air cavity and the resonance of solid platform make something not completely horrible. Lost power once and placed it at the mouth of an empty kleenex box just for giggles, amazing what an air cavity can do.

 

[carbonzit]

You don't have to guess the impedance of a speaker, all you need is a multimeter set to measure low ohmic resistance.

"Ohmic resistance"??? That's like saying "ATM machine" or "PIN number" or ... any number of redundant things. I'm always a bit amused when people use it, Moderated OFF TOPIC

Resistance is ... resistance. (Or you could say it's futile, if you're a fan of a certain sci-fi series.)

Sorry, couldn't resist.

 

[Sceadwian]

What's to resist? You simply do not know. The complex resistance of those speakers will change dramatically over the full spectrum of their output based on the inductance and capacitive effects (primarily the inductance). If you think resistance is 'simple' you've cracked before you started, and obviously don't know a thing about impedance.

There is ohmic resistance there is inductive resistance, and there is capacitive resistance, all three are non linear in the real world, all three and more form complex impedance.

 

[carbonzit]

There is ohmic resistance there is inductive resistance, and there is capacitive resistance, all three are non linear in the real world, all three and more form complex impedance.

Moderated OT.

There's capacitive and inductive reactance, sure. And there's AC impedance. But "resistance", so far as I know, unless someone has recently redefined it, simply means plain old DC resistance. And so far as I know, nobody who knows what they're talking about will use the two terms (reactance and resistance) interchangeably. Am I not correct?

A speaker may have an impedance of 8 ohms, but a DC resistance of only 6.5 ohms. Or whatever.

 

[Sceadwian]

Or whatever.

Sorry, typically in a speaker setup the impedance is a direct match to the DC resistance.

 

[carbonzit]

Sorry, typically in a speaker setup the impedance is a direct match to the DC resistance.

[/quote]

Which is nicely covered by "whatever", dontcha think? (It was an example, son.)

 

[Sceadwian]

The example posted had no practical considerations so I'm sorry it failed utterly at being one. "or whatever" doesn't cover anything, except that you have no idea of what you're talking about.

 

[audioguru]

"Cell phones have low power small "speakers" like that. They produce squeaky sounds with no low frequencies."

audioguru, I am publicly upset with your statement as such is not the case, and your name being 'audioguru' you should know better than making such broad misleading statements especially to someone trying to learn something, provide information or keep your negativity to yourself.

I know what earphones laying on a table sound like. Just high frequency squeaks. The tiny speakers can move the very small amount of air from them to your ears but in the open they produce NO bass frequencies. Cell phones are the same.

That speaker WILL produce solid low frequencies in the same power output range as it does it's mid and high tones IF it's put in the proper speaker cabinet, which would be many times larger than the speaker for free air speakers.

My first computer was a Compaq with tiny speakers built into the monitor. The drivers had a paper cone and were an oval 2" long by 1" wide in base-reflex (ported) enclosures. They produced pretty good but not loud sounds down to about 100Hz so no deep bass.
My son burned one speaker with feedback noise and it was replaced under warranty.

Them being headphone drivers they did produce bass, because the air cavity between the ear muff and the ear itself acted as the resonant cavity.

No.
The tiny air volume between an earphone and your ears would resonate at a pretty high frequency but does not resonate. The tiny air volume behind the little speakers would resonate at a pretty high frequency but it also does not resonate.
The tiny drivers don't have enough mass (weight) to resonate.

The tiny drivers can move the small volume of air between them and your ears down to very low frequencies.
But in the open (like a speaker) they produce NO bass.

 

[carbonzit]

The example posted had no practical considerations so I'm sorry it failed utterly at being one. "or whatever" doesn't cover anything, except that you have no idea of what you're talking about.

BS. I pointed out your misuse of the term "resistance" when applied to capacitance or inductance, when what you should have used was "reactance".

I don't know everything about electronics, but I do know that much.

If you find errors in what I posted and want to point them out, be my guest.

 

[neptune]

can these three speakers work as mic.
i want to use them as microphone , i will use amplifier built by BC547 transistors (maybe darlington). then output will be same speaker (Big one),
what will be the current produced by big speakers when someone speaks into them , can it be amplified , or will i have to buy new microphone ?

 

[neptune]

A speaker may have an impedance of 8 ohms, but a DC resistance of only 6.5 ohms. Or whatever.

how so ? , why would speaker like that given in picture would have DC resistance

 

[audioguru]

A speaker resonates which causes it to sound "boomy" when used as a microphone. Like the extremely cheap intercoms at gas stations.
Use an inexpensive electret mic which will sound perfect.

 

[RODALCO]

I always believed that the speaker impedance test was measured with a 1000 Hz test signal.
As audio frequencies change between 20 and 20,000 Hz the reactance of the speaker coil does change too.

For example an 8 ohms speaker coil has that value at 1000 Hz.
The DC coil resistance will be a lot less, that also backs up the fact that when an amplidier output elco goes the DC usually burns out the connected speakers.

Just my $0.02 on this topic.

 

[Sceadwian]

There are no such standards I've ever found Rodalco. Every speaker that has a rating printed on it is within spitting distance of it's DC ohmic resistance, that I've measured excluding those types of speakers that don't have simple DC resistances that can be measured such as piezo speakers. If you can find 4 ohm speakers that measure a DC resistance of .25 ohms I'd love to see em.

carbonzit, please look up the definition of reactance, there is no BS going on here at all. Capacitive reactance and capacitive resistance are both dictionary valid methods of defining resistance to flow. Sure it's slightly inappropriate language from a technical standpoint and I'll admit that gladly as to the words I should have used but it invalidates absolutely nothing of what I've said so far from a functional perspective. The error in your post is the language is irrelevant to what I was describing in this particular case.

I'm sorry Audioguru but you're wrong, modern cell phones designed for audio have come a long way, especially with audio, I consider bass 20hz to 300hz. My cell phone has solid audible output at 150hz. I'm not sure what relation to the current post your son burning out paper cone speakers from a Compaq has to do with this thread.

No.
The tiny air volume between an earphone and your ears would resonate at a pretty high frequency but does not resonate. The tiny air volume behind the little speakers would resonate at a pretty high frequency but it also does not resonate.
The tiny drivers don't have enough mass (weight) to resonate.

I can empirically prove that wrong, I've frequency tested over ear muffle (non ported) headphones that produce bass down to 30hz or so. Try a modern pair of in ear headphones and you'll be even more wrong, I've tested in ear headphones and found I could tell the pressure difference down to close to 10hz, when I alternated the phase between left and right ears even at low volumes the resonance was so bad that it caused me to rip the headphones out.

 

[carbonzit]

carbonzit, please look up the definition of reactance, there is no BS going on here at all. Capacitive reactance and capacitive resistance are both dictionary valid methods of defining resistance to flow. Sure it's slightly inappropriate language from a technical standpoint and I'll admit that gladly as to the words I should have used but it invalidates absolutely nothing of what I've said so far from a functional perspective. The error in your post is the language is irrelevant to what I was describing in this particular case.

You have a mighty funny (and a mighty roundabout) way of saying "I was wrong". But I accept it nonetheless.

 

[neptune]

so can i use them as microphone , the small one is out of headphone. i dont care about voice quality , it should just be audible.
what will be the current produced by big speakers when someone speaks into them , can it be amplified , or will i have to buy new microphone ?
how can a speaker have DC resistance when it is just a winding of wire along a magnet ?